Optimization of temperature swing strategy for selective cooling crystallization of alpha-form L-glutamic acid crystals

Abstract

L-glutamic acid can be crystallized as metastable alpha-form and stable beta-fonn crystal. The alpha-form is desired because of its prismatic shape. Production of alpha-form of L-glutamic acid by cooling crystallization is not well-defined and alpha-form solid is commercially not available. In this study, an optimal cooling strategy to selectively produce large and narrowly distributed alpha-crystals is found by modeling and optimizing the crystallization and polymorphic transformation of L-glutamic acid. The optimal temperature profile is found to be cooling-heating-cooling concept where short nucleation period is followed by growth period in metastable zone. The obtained alpha-form of L-glutamic acid by optimal strategy had improved mean size, distribution, and purity compared to constant cooling.